On the alignment and axisymmetrization of a vertically tilted geostrophic vortex

1995 ◽  
Vol 289 ◽  
pp. 29-50 ◽  
Author(s):  
F. Viera
Keyword(s):  
Cross Sections ◽  
Three Dimensional ◽  
Boundary Surface ◽  
Density Stratification ◽  
Uniform Density ◽  
General Tendency ◽  
Cylindrical Shape ◽  
Vertical Alignment ◽  
Horizontal Scale ◽  
Geostrophic Vortex

We investigate the evolution of a vertically tilted geostrophic vortex of cylindrical shape and circular horizontal cross-section using the recently developed method of boundary surface dynamics. The vortex consists of a finite volume of constant potential vorticity immersed in a spatially unbounded fluid of uniform density stratification. The fully nonlinear three-dimensional problem is then reduced to the calculation of the Lagrangian evolution of the boundary surface of the vortex region, thus decreasing the dimensionality by one. In the numerical simulations presented here, the vortex shows a general tendency to attain vertical alignment and a horizontal axisymmetrical shape by wobbling about its centre and going through three basic stages of evolution: (a) the circular horizontal cross-sections of the upper and lower parts of the vortex distort and become elongated; (b) the upper and lower sections then become vertically aligned by reducing their horizontal intercentroid distances; and (c) the distorted horizontal cross-sections relax towards axisymmetry, often through the process of filamentation. For a given vortex height, if the horizontal scale of the flow is close to the internal radius of deformation, or equivalently, the density stratification is not too strong, the processes of filamentation and vertical alignment are enhanced. However, for stronger stratifications, both filamentation and vertical alignment are found to be greatly inhibited. For relatively small initial inclination angles, filamentation only occurs in the upper and lower sections of the vortex. Increasing the angle of tilt also increases the tendency of the surface to steepen and filament in the middle sections of the vortex. For a fixed value of the ratio of horizontal scale of the flow to the deformation radius, taller vortices have an increased tendency to align and axisymmetrize than shorter vortices of equal inclination angle.

Stratification effects on the stability of columnar vortices on the f-plane

1998 ◽  
Vol 355 ◽  
pp. 45-79 ◽  
Author(s):  
P. G. POTYLITSIN ◽  
W. R. PELTIER
Keyword(s):  
Cross Sections ◽  
Laboratory Experiments ◽  
Three Dimensional ◽  
Oceanic Islands ◽  
Density Stratification ◽  
Centrifugal Instability ◽  
Vortex Streets ◽  
Explicit Analysis ◽  
Karman Vortex ◽  
The Stability

We consider the stability with respect to three-dimensional perturbations of columnar vortices on the f-plane and as a function of the strength of a stabilizing density stratification parallel to the axis of the vortex. We seek to understand the dynamics of the processes through which such a vertically oriented barotropic vortex may be destabilized. As models of the basic vorticity distribution we consider both Kelvin–Helmholtz vortices in shear and ‘Kida-like’ vortices in strain. In the case of rotating unstratified flow, an isolated anticyclonic vortex column is shown to be strongly destabilized to three-dimensional perturbations by small values of the background rotation, while rapid rotation strongly stabilizes both anticyclonic and cyclonic columns, as expected on the basis of the Taylor–Proudman theorem. The dominant instability mechanism which drives the destruction of anticyclonic vortices in the presence of slow background rotation may be understood to constitute a three-dimensional inertial (centrifugal) instability. Through explicit analysis we show that sufficiently strong density stratification stabilizes the two-dimensional columnar structures to disruption by this and additional modes of instability that exist even in the absence of rotation. We furthermore demonstrate that there exists a second fundamental mode of instability in the presense of background rotation which affects only anticyclonic vortex columns whose cross-sections are elliptical. Only when the ellipticity of the vortex is sufficiently high does this mode dominate the centrifugal mode. The process whereby anticyclonic vortices may be selectively destroyed appears to provide a possible explanation of an asymmetry that is sometimes observed to be characteristic of the atmospheric von Kármán vortex streets that are observed in the lee of oceanic islands. The anticyclonic branch of the street often seems to be absent. More generally, the centrifugal mechanism for the selective destruction of anticyclones discussed herein very clearly explains a number of recent results obtained from both laboratory experiments and numerical simulations.

scholarly journals Taking into account camera tilt when correcting a three-dimensional model of a hollow pipe during visual diagnostics with a self-propelled complex

2020 ◽  
Vol 224 ◽  
pp. 02014
Author(s):  
E Petrenko ◽  
R Kornilov ◽  
V Dolgov ◽  
E Lukianov
Keyword(s):  
Cross Sections ◽  
Three Dimensional ◽  
Longitudinal Section ◽  
Cylindrical Shape ◽  
Dimensional Model ◽  
Point Model ◽  
Three Dimensional Model ◽  
Model Based ◽  
Section Profile

This paper investigates the problem of assessing the degree of pipe deformation and the deviation of its longitudinal section profile from a cylindrical shape based on a three-dimensional point model of a hollow pipe under conditions when this model turns out to be displaced (rotated in space) relative to its real position. An algorithm for correcting a three-dimensional point model based on data on the current tilt of the camera is considered, as well as an algorithm for the actually obtained image overlaid with virtual cross-sections of the pipe, close to ideal.

Geological Field Sketches and Illustrations

2019 ◽  
Author(s):  
Matthew J. Genge
Keyword(s):  
Cross Sections ◽  
Earth Science ◽  
Three Dimensional ◽  
Worked Examples ◽  
Scientific Publications ◽  
Thin Sections ◽  
Geological Features ◽  
Different Types ◽  
The Subject

Drawings, illustrations, and field sketches play an important role in Earth Science since they are used to record field observations, develop interpretations, and communicate results in reports and scientific publications. Drawing geology in the field furthermore facilitates observation and maximizes the value of fieldwork. Every geologist, whether a student, academic, professional, or amateur enthusiast, will benefit from the ability to draw geological features accurately. This book describes how and what to draw in geology. Essential drawing techniques, together with practical advice in creating high quality diagrams, are described the opening chapters. How to draw different types of geology, including faults, folds, metamorphic rocks, sedimentary rocks, igneous rocks, and fossils, are the subjects of separate chapters, and include descriptions of what are the important features to draw and describe. Different types of sketch, such as drawings of three-dimensional outcrops, landscapes, thin-sections, and hand-specimens of rocks, crystals, and minerals, are discussed. The methods used to create technical diagrams such as geological maps and cross-sections are also covered. Finally, modern techniques in the acquisition and recording of field data, including photogrammetry and aerial surveys, and digital methods of illustration, are the subject of the final chapter of the book. Throughout, worked examples of field sketches and illustrations are provided as well as descriptions of the common mistakes to be avoided.

scholarly journals Thermo-Hydraulic Performance of U-Tube Borehole Heat Exchanger with Different Cross-Sections

2021 ◽  
Vol 13 (6) ◽  
pp. 3255
Author(s):  
Aizhao Zhou ◽  
Xianwen Huang ◽  
Wei Wang ◽  
Pengming Jiang ◽  
Xinwei Li
Keyword(s):  
Heat Transfer ◽  
Heat Exchange ◽  
Heat Resistance ◽  
Cross Sections ◽  
Three Dimensional ◽  
Thermal Response ◽  
Transfer Efficiency ◽  
Cross Sectional ◽  
Heat Transfer Efficiency ◽  
Oval Tube

For reducing the initial GSHP investment, the heat transfer efficiency of the borehole heat exchange (BHE) system can be enhanced to reduce the number or depth of drilling. This paper proposes a novel and simple BHE design by changing the cross-sectional shape of the U-tube to increase the heat transfer efficiency of BHEs. Specifically, in this study, we (1) verified the reliability of the three-dimensional numerical model based on the thermal response test (TRT) and (2) compared the inlet and outlet temperatures of the different U-tubes at 48 h under the premise of constant leg distance and fluid area. Referent to the circular tube, the increases in the heat exchange efficiencies of the curved oval tube, flat oval tube, semicircle tube, and sector tube were 13.0%, 19.1%, 9.4%, and 14.8%, respectively. (3) The heat flux heterogeneity of the tubes on the inlet and outlet sides of the BHE, in decreasing order, is flat oval, semicircle, curved oval, sector, and circle shapes. (4) The temperature heterogeneity of the borehole wall in the BHE in decreasing order is circle, sector, curved oval, flat oval, and semicircle shapes. (5) Under the premise of maximum leg distance, referent to the heat resistance of the tube with a circle shape at 48 h, the heat exchange efficiency of the curved oval, flat oval, semicircle, and sector tubes increased 12.6%, 17.7%, 10.3%, and 7.8%, respectively. (6) We found that the adjustments of the leg distance and the tube shape affect the heat resistance by about 25% and 12%, respectively. (7) The flat-oval-shaped tube at the maximum leg distance was found to be the best tube design for BHEs.

scholarly journals The Numerical Analysis of the Flow on the Smooth and Nonsmooth Boundaries by IBEM/DBIEM

2019 ◽  
Vol 2019 ◽  
pp. 1-14
Author(s):  
Gang Xu ◽  
Guangwei Zhao ◽  
Jing Chen ◽  
Shuqi Wang ◽  
Weichao Shi
Keyword(s):  
Boundary Value ◽  
Three Dimensional ◽  
Boundary Surface ◽  
Tangential Velocity ◽  
Integral Equation Method ◽  
Boundary Integral ◽  
Surface Shape ◽  
Normal Vector ◽  
Computational Domain ◽  
Nonsmooth Boundary

The value of the tangential velocity on the Boundary Value Problem (BVP) is inaccurate when comparing the results with analytical solutions by Indirect Boundary Element Method (IBEM), especially at the intersection region where the normal vector is changing rapidly (named nonsmooth boundary). In this study, the singularity of the BVP, which is directly arranged in the center of the surface of the fluid computing domain, is moved outside the computational domain by using the Desingularized Boundary Integral Equation Method (DBIEM). In order to analyze the accuracy of the IBEM/DBIEM and validate the above-mentioned problem, three-dimensional uniform flow over a sphere has been presented. The convergent study of the presented model has been investigated, including desingularized distance in the DBIEM. Then, the numerical results were compared with the analytical solution. It was found that the accuracy of velocity distribution in the flow field has been greatly improved at the intersection region, which has suddenly changed the boundary surface shape of the fluid domain. The conclusions can guide the study on the flow over nonsmooth boundaries by using boundary value method.

scholarly journals Computer-aided design of multi-purpose steel headframes for mines with a new technical level

2020 ◽  
Vol 174 ◽  
pp. 01048
Author(s):  
Elena Kassikhina ◽  
Vladimir Pershin ◽  
Nina Rusakova
Keyword(s):  
Cross Sections ◽  
Computer Aided Design ◽  
Information Technologies ◽  
Three Dimensional ◽  
Numerical Control ◽  
Technical Level ◽  
Resource Saving ◽  
Existing Structures ◽  
Set Up ◽  
Aided Design

The existing structures of the steel sinking headgear and permanent headframe do not meet the requirements of resource saving (metal consumption and manpower input at installation), and the present methods of the headframe designing do not fully reflect recent possibilities of applying of the advanced information technologies. Technical level of the modern software makes it possible for designers to set up multiple numerical experiments to create a computer simulation that allows solving the problem without field and laboratory experiments, and therefore without special costs. In this regard, a mathematical simulation has been developed and based on it, software to select cross-sections of multi- purpose steel headframe elements and to calculate proper weight of its metal structures depending on the characteristics and hoisting equipment. A headframe drawing is displayed, as the results of the software work, including list of elements, obtained optimal hoisting equipment in accordance with the initial data. The software allows speeding up graphic work and reducing manpower input on calculations and paper work. The software allows developing a three-dimensional image of the structure and its functional blocks, based on the obtained initial parameters, as well as developing control software for units with numerical control (NC) in order to manufacture multi-purpose headframes.

Analysing the Natural Resting Aspects of a Component for Automated Assembly

1995 ◽  
Vol 209 (2) ◽  
pp. 125-131 ◽  
Author(s):  
B K A Ngoi ◽  
L E N Lim ◽  
S S G Lee ◽  
S W Lye
Keyword(s):  
Cross Sections ◽  
Computer Aided Design ◽  
Energy Barrier ◽  
Three Dimensional ◽  
Rectangular Prism ◽  
Automatic Assembly ◽  
Automated Assembly ◽  
Barrier Method ◽  
Aided Design ◽  
Natural Resting Aspect

This paper proposes the construction of an energy envelope that can be used to advantage with the energy barrier method to analyse the natural resting aspect of engineering parts destined for automatic assembly. Unlike the energy barrier method, the energy envelope does not require any visualization of the projection of the energy barrier on the aspect of interest. The energy envelope is the three-dimensional topology of the changes in height of the centroid, as the part attempts changes of aspect. The paper describes how it may be computed in a CAD (computer aided design) solid modeller. The results of applying the energy envelope to prisms of square and cylindrical cross-sections are the same as those predicted by the energy barrier method. When extended to the analysis of a rectangular prism, the results were consistent with Boothroyd's dynamic solution and Boothroyd's experimental data. This conclusion is encouraging as there is no irrefutable evidence that the energy barrier method may be applied to the analysis of the rectangular prism.

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